A commonly used rotary bending tool of the type with which the present invention is particularly useful is described in U.S. Pat. No. 5,341,669, issued Aug. 3, 1994. According to recognized practice a rotary bending tool of this type is frequently used in a brake type press where forming action of the bending tool involves a combination of rotation and translation movements.
Such bending tools normally are held in a tool holder by machine screws inserted into bored or tapped aligned bores in the bending tool and tool holder. Great care must be taken to insure that a bending tool cut to a desired length (depending on the press involved) fits the press so that mounting holes in the bending tool unit align properly with corresponding bored and tapped holes in the tool holder.
A precision keyway is usually cut in the tool holder to which the bending tool is to be attached. Any key fitted into such a keyway must be secured positively to avoid any possibility of falling out during operation which could result in serious damage to the forming die, the press, and likely the operator.
Rotary benders conventionally come in several sizes for use with work materials having a wide range of thicknesses. However, the bending tools are quite limited to maximum lengths. Thus when used in a press brake it is often necessary to abut several short bending tool sections together in order to achieve the overall length required. Such use of several short tool lengths further compounds the problem of maintaining close tolerances necessary to mate the mounting holes in the bending tool with the mounting holes in the tool holder. This problem of hole alignment is further complicated by the many different hole patterns used in rotary benders, depending on the overall length of the bender unit. Thus for instance a tool 24" long cannot be replaced by two 12" pieces, because of hole pattern differences. It is to be noted that currently 36 inches is the maximum length available for rotary benders of larger sizes. Smaller sizes most commonly used are only available in 24 inch maximum lengths. The most common length of press brake application is twelve feet.